TOKYO — North Korea has threatened to restart the development of its nuclear weapons program unless the United States lifts sanctions, underscoring one of the major potential stumbling blocks in Washington’s diplomatic outreach to North Korean leader Kim Jong Un.

The Trump administration has insisted that sanctions and other pressures remain on North Korea until it dismantles its nuclear program. Kim’s regime, however, has always demanded a step-by-step process of denuclearization that would include lifting U.S. sanctions along the way.

In the past month, Pyongyang has stepped up its calls for sanctions relief. The statement released late Friday by its Foreign Ministry is the latest indication that negotiations over the nuclear program have hit an impasse.

The issue of sanctions has also created a rift between Seoul and Washington.

South Korea has backed the North’s call for sanctions relief and is keen to get moving on an ambitious program of economic development and cooperation, including building road and rail links across the countries’ heavily militarized frontier.

The North Korean Foreign Ministry warned that unless sanctions were lifted and Washington stopped behaving “arrogantly,” North Korea could reinstate “pyongjin” — its policy of simultaneously developing its nuclear weapons program alongside seeking economic development.

In April, Kim declared that the country’s nuclear weapons program was sufficiently advanced and that “pyongjin” would be replaced by a focus on improving the economy. Backtracking could reignite tensions with the United States.

Still, neither side has turned its back on negotiations.

Secretary of State Mike Pompeo told journalists he will meet his North Korean “counterpart” for further talks in the coming week, although he did not specify exactly when, where or with whom those talks would take place.

Pompeo met Kim last month in Pyongyang, and he says he secured a promise to allow American inspectors into two nuclear and missile testing sites to check on their dismantlement.

Speaking on “The Laura Ingraham Show” in the past week, Pompeo said a summit between Kim and President Trump could happen early next year and enable “a substantial breakthrough in taking down the nuclear threat from North Korea.”

“We’re still happy that they ­haven’t conducted a nuclear test in an awfully long time and they haven’t launched a missile in an awfully long time,” Pompeo said, adding that Kim had made clear to him that he intends to denuclearize but that much more work needs to be done.

In an interview Friday with Sean Hannity on Fox News, Pompeo reiterated that “a lot of work” remains to be done, adding: “I’m confident that we will keep the economic pressure in place until such time as Chairman Kim fulfills the commitment he made to Trump back in June in Singapore.”

To Pyongyang, that oft-repeated refrain about pressure is the problem. North Korea says Trump promised Kim in June that a new era in relations was beginning.

“The improvement of relations and sanctions are incompatible,” the Foreign Ministry said. “ ‘Friendship’ is incompatible with ‘pressure.’ ”

The Foreign Ministry asked Washington to abandon its “foolish daydream” that sanctions and pressure will lead to denuclearization. “We cannot help laughing at such a foolish idea,” it said.

The United States, it added, was making a mistake if it believed North Korea would agree to unilateral disarmament with sanctions in place, and it said negotiations should be “simultaneous and phased” and based on “reciprocity and equality.”

“If the U.S. keeps behaving arrogantly without showing any change in its stand, while failing to properly understand our repeated demand, the DPRK may add one thing to the state policy for directing all efforts to the economic construction adopted in April and as a result, the word ‘pyongjin’ may appear again,” the statement said, using the common abbreviation of North Korea’s official name, the Democratic People’s Republic of Korea.

“The U.S. will be able to dodge piteous future that may do harm to itself and the world only when it gives up highflying desire and one-sided viewpoint,” the statement said.